Vascular diseases are prevalent worldwide. Bypass surgery, whereby a conduit, either artificial or autologous, is grafted into an existing vessel to circumvent a diseased portion of the vessel or to restore blood flow around a blocked or damaged blood vessel, is one of the most common treatments for such diseases.
Vascular grafts are also used as entry sites in dialysis patients. The graft connects or bridges an artery to a vein in the patient's body. A needle is inserted into the graft, allowing for blood to be withdrawn and passed through a hemodialysis machine and returned to the patient through a second needle inserted into the graft.
A significant number of by-pass grafts fail within 5 to 7 years. The average life-span for hemodialysis grafts is even shorter, often less than two years. A primary cause of graft failure is the closing of the graft due to tissue in-growth and eventually thrombosis formation. The smaller the graft diameter, the higher the graft failure rate. The lost patency resulting from graft closure or collapse is particularly problematic at the outflow site where the outflow end of the graft touches the vessel.
However, this issue has not been adequately addressed by conventional techniques to restore patency, which typically include surgical procedures (e.g., thrombectomy or percutaneous thrombectomy) or chemical intervention techniques (e.g., administration of anti-clotting or anti-platelet drugs, such as ticlopidine, aspirin, dipyridimole, or clopidogrel) to remove ingrown tissue or clotting that otherwise contributes to graft failure. In particular, surgical and chemical interventions can introduce unnecessary risk (e.g., of infection, bleeding, etc.) and often are inadequately effective to maintain patency over longer periods of time.
Thus, there is a need for a graft for which patency can be restored easily after implantation without requiring risky and ineffective chemical or surgical interventions. There is also a need for different graft structures that utilize various features of the graft technologies disclosed herein.